Non-Conventional Time Domain (TD)-NMR Approaches for Food Quality: Case of Gelatin-Based Candies as a Model Food

The TD-NMR technique mostly involves the use of T1 (spin-lattice) and T2 (spin-spin)
relaxation times to explain the changes occurring in food systems. However, these relaxation times
are affected by many factors and might not always be the best indicators to work with in food related
TD-NMR studies. In this study, the non-conventional TD-NMR approaches of Solid Echo
(SE)/Magic Sandwich Echo (MSE) and Spin Diffusion in food systems were used for the first time. Soft
confectionary gelatin gels were formulated and conventional (T1) and non-conventional (SE, MSE and
Spin Diffusion) TD-NMR experiments were performed. Corn syrups with different glucose/fructose
compositions were used to prepare the soft candies. Hardness, °Brix (°Bx), and water activity (aw)
measurements were also conducted complementary to NMR experiments. Relaxation times changed
(p < 0.05) with respect to syrup type with no obvious trend. SE/MSE experiments were performed to
calculate the crystallinity of the samples. Samples prepared with fructose had the lowest crystallinity
values (p < 0.05). Spin Diffusion experiments were performed by using Goldman–Shen pulse sequence
and the interface thickness (d) was calculated. Interface thickness values showed a wide range of
variation (p < 0.05). Results showed that non-conventional NMR approaches had a high potential to be
utilized in food systems for quality control purposes.